The present invention relates generally to systems for radiating heat from spacecraft or the like, and more particularly to a variable, deployable heat exchange radiator for a spacecraft providing high peak to average heat rejection.
The profile of a power demand duty cycle of a space mission may include periods of high power draw over short times interspersed with much longer periods when power is needed at only a low level. The pulse duration, amplitude and frequency are determined by mission applications. Conventional spacecraft radiators are sized to reject peak power waste heat loads, and turned down to reject power loads during off peak portions of a duty cycle. Conventional radiators are capable of near constant load thermal control over a range of nominally 10:1 peak to average heat loads for steady state head rejection. However, for high power applications requiring high peak to average heat rejection capability wherein system weight is constrained, conventional radiator designs are of limited utility.
The present invention is a variable volume and surface area deployable heat exchange radiator utilizing a two-phase heat exchange system to take advantage of the high boiling heat transfer rate of a heat exchange medium at a heat source. The invention is characterized by a high condensation heat transfer rate inside the radiator, low operating fluid mass due to the large latent heat of vaporization, and high radiator effectiveness due to near isothermal operation. The invention stores substantial heat energy during a peak power load portion of the duty cycle for rejection of the stored heat during the off peak portion of the cycle. The invention is desirable for waste heat rejection where the peak to average heat generation is large, i.e., greater than about 5:1, and can be sized for average duty cycle heat rejection and storage of peak power spikes for dissipation during off peak periods. The invention may be selectively structured for an operating temperature of 300.degree. K. (low temperature electronic cooling regime), to about 1000.degree. K. (space power system heat rejection regime).
For modest peak to average (e.g., to about 100:1) heat loads, a high surface area to volume rollout configuration is described. For higher peak to average ratios (e.g., to about 10.sup.4 :1), an inflatable bag or bellows radiator structure having large volume to mass ratio is described. The radiator is constructed of low mass, thin flexible material which can be collapsed and stored, and which can be expanded readily when high peak power heat loads are imposed. The bellows structure can take in large amounts of vapor during the peak (pulse) portion of the duty cycle, and reject the waste heat through condensation and radiation during the off peak portions of the duty cycle. The invention therefore provides a light weight radiator which is compact and easily protected from micrometeoroid impact except during peak expanded operation, and has minimum overboard contamination problems because the heat exchange medium is contained and recycled, rather than expelled overboard.
It is a principal object of the invention to provide a pulsed power heat rejection system for spacecraft or like vehicles.
It is a further object of the invention to provide a recycling heat rejection system having high peak to average heat rejection capability.
It is yet another object of the invention to provide a light weight, non-contaminating, expandable heat radiator having high peak to average heat rejection capability.
These and other objects of the invention will become apparent as the description of representative embodiments proceeds.